The present invention relates to hot film anemometers particularly for exhaust gas recirculation (EGR) systems. A hot film anemometer determines the mass of the mass flow, for example an exhaust gas flow, via the energy consumption of a resistance layer arranged on a substrate in a mass flow. For the more precise controlling of an EGR, two resistors thermally decoupled from one another are introduced into the exhaust gas flow. For this purpose, this flow sensor is fastened to an exhaust gas channel. In and on the exhaust gas channel, the flow sensors are exposed to temperatures between 200° C. and 300° C. For use in this temperature range, a sensor tip is provided made of inorganic materials.
An anemometer has two heating resistors thermally decoupled from one another, or has one heating resistor and one measuring resistor according to European patent application publication EP 1 151 188 A0.
For the self-cleaning of a flow sensor element in which a temperature measuring element and a heating element are arranged on a carrier element, according to German published patent application DE 10 2005 051 182 A1, the temperature measuring element is heated with an additional platinum thin-film resistor.
German published patent application DE 10 2006 030 786 A1 and International patent application Nos. WO 2007/048573 A1, and WO 2008/000494 A2 disclose flow sensors in which electrical cables lead into a metal pipe, which is sealed by a cover into which film resistors are plugged.
With an arrangement of a film resistor in an exhaust pipe or exhaust gas recirculation pipe according to International patent application publication No. WO 2008/131890 A2, the film resistor is fastened in a carrier, which is sealed against a shielding (4a) or a housing (4b), which is connected tightly to the exhaust pipe or exhaust gas recirculation pipe, and is wherein the carrier (3) and the shielding or the housing are sealed against one another radially outside the exhaust pipe or exhaust recirculation pipe at a distance therefrom. German published patent application DE 10 2008 037206 A1 discloses an anemometric measuring device in an exhaust recirculation pipe, in which a ceramic carrier, on which film resistors are fastened, is embedded in an injection-molded housing made of plastic, wherein the electrical connection is led through the injection molding and sealed and fastened inside the injection-molded part.